The compounds of the invention can be prepared by methods analogous to those described by Pollak et al., Tetrahedron 22, 2073 (1966). Other methods are described in Miller and Rose, J. Chem, Soc. 1963, 5642: Basu and Rose, J. Chem. Soc. 1963, 5660 (1963); and Davies et al., Nature, 234 50 (1971).
The compound 3-morpholino-6-methyl-8-phenyl-s-triazolo[4,3-b]pyridazine was described by Yurugi et al., Takeda Kenkyusho 32 (2) , 111-117 (1973). Other morpholino triazolopyridazines are described in French Pat. No. 1248409 and in Chemical Abstracts, 67 21884q.